Shaft gauge



. April 1952 c. T. WALLIS ,591,895

SHAFT GAUGE Filed Aug. 51, 1949 Patented Apr. 8, 1952 i Cyril 'IL WaIHs; Brockport, N. Y.-, assignor to Gen-- .erakMotoraCorporation, Detroit, Mich., a corporatlomof :Delaware Application Augus'ti31,"1949, Serial No. 113,364

1: Claim. 1

This invention relates to a gauge construction which is particularly adapted for measuring or checking the diameter of relatively small" shafts.

The-principal object of the invention is to provide a simple gauge ofextreme accuracy which can, however, be readily'constructed of parts a that requireonly-such manufacturing tolerances as H can bec easily maintained during fabrication.

The above togetherwith otherobjects and the advantages of the present invention will be apparent fromorspecifically noted in the following description of the embodiment shown in the accompanying drawing.

Fig. 1 is an end; view; ofthe; present: gauge; with a shaft to be gauged shown inycross, section.

Fig. 2 is a side view ofthe vgauge with parts broken away and in section substantially on line 2-2 of-Fig. 1 showing an article havinga shaft to be gauged" in elevation.

Fig. 3 is a diagram used-in the; development of an equation to predeterminetha constructional dimensions for gauges of various sizes.

The present gauge consists essentially of three rollers or cylinders which are preferably of equal diameters and held or clamped together so that ll they touch each other to form an opening having three inwardly curved sides within which the shaft or other article to be gauged .is, to be inserted. As will be noted hereinafter, the diameter of a circle inscribed in this opening and touching all three sides is a function of the outhexagonal rod I2 having an axial bore M to loosely receive the cylinder 4. The bore [4 is enlarged and formed with a tapered socket l6 at its upper end to receive a split tapered clamping ring or collar I8 which may be forced into the tapered socket around the cylinders and secured by set screw 20 to clamp and maintain the cylinders 4 in perfect contact with each oth- With. this gauge construction. the cylinders 4 can be'rotatablyadjusted' as they wear to present new surfaces for engagement by the articles to be gauged, and the cylinders are also of such 'lengththat. they. can vbeaxially adjusted in .the gauge body and the. used; or worn end portions ground off. or otherwise; removed. l

I In. using} the .pre'sentgauge. it has been heretofore noted that the shaft. or similar round. article is adapted to be inserted within the gauge opening 6. Since this opening is formed or constituted by. the inwardly. curved sides. ofthelcylinders 4, it willbe seen-thatthere arethree points of contact ontthe shaft. beingv gauged and-any shaft-which isnot truly roundcan thus be read- 11y. detected.

It willbe apparent that thisgauge. is of simple .construction andthat .the only dimensions: which are: at all critical. to insure extreme accuracy are therespectivediametersof the three cylinders 4. 'Ihesecylinders are preferably of equaldiam- .eters and a formula or eql ationcan be readily developed to determine the proper cylinder diameter for gauging shafts of any given diameter.

ent embodiment the gauge bodyconsists of a a In the diagram of Fig. 3, the gauge cylinders 4 having diameter D1 are shown in contact with each other to form the opening 6 and the circle of the diameter D2 which can be inscribed in this opening to touch all three cylinders is designated by numeral 8 since it corresponds to the shaft to be gauged by insertion within the opening 6 as heretofore described. The centers A, B and C of the respective cylinders are connected to form an equilateral triangle and a line AE' is drawn to bisect the angle BAC of this triangle. through the center F of the circle 8 and through a point G at which this circle contacts the cylinder having the center A. Two similar right triangles are-formed by dropping perpendiculars to the line AC from the center F and point'G, respectively, and it will be noted that the triangle having base bi has a hypotenuse Ci equal to the cylinder radius while the other triangle has a base be equal to the cylinder radius and a hypotenuse cz equal to the cylinder radius plus the radius of circle 8.

Referring to this diagram the equation for determining the proper diameterfor the gauge cylinders may be developed as follows:

Since the anglesof the two right triangles It will be seen that the line AE passes,

which are constructed as indicated above are equal, their corresponding sides are proportional, so

-El b, b, The side fb1=ci cos angle EAC=ci cos 30-=c1(.8660) and substituting in the above equation, we have The diameter of the circle 8 or D2=2(O2O1) and since cr=b2, we find by substitution that D,= 2( -b,) 21 1)= 2b,(. 15 473) In this equation 2b2=Dl so Dg=D1(.15473) and the final equation for determining the diameter D1 of the gauge cylinders is therefore The foregoing equation has been developed not only to enable those skilled vin the art to can be easily ground to an accuracy of .0001 inch ,7 and the accuracy of the inscribed circle will therefore be approximately one-sixth of this figure, or .000015 inch.

In the illustration given above the three gauge cylinders have been assumed to be of equal diameters and, while this may be preferable from the standpoint of manufacture and assembly, it will be understood that this is not essential in the broader aspects of the invention. If, for instance, two of the cylinders be assumed to be of equal diameters. the third may be one of a series of interchangeable cylinders of varying diameters computed to give a desired range of gauge openings.

When three cylinders are held incontact with each other to form the gauge opening it will be apparent that the size of the gauge opening is in all instances a function of the diameters of the cylinders. Although only a specific embodiment has been shown and described herein, it will be understood that modifications and changes in the details of construction will be obvious to those skilled in the art and are contemplated as within the scope of the present invention as defined in the claim appended hereto.

I claim: I

In a gauge for shafts or the like, a body, three parallel cylinders of substantially equal diameters mounted in said body, and clamping means between said body and cylinders to en- CYRIIL T. WAILIS.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 195,008 Harvey Sept. 11, 1877 2,362,907 -Levin'i;. NOV; 14, 1944 2,392,317

.Eisele Jan. 8, 1946 

